Our proposed work is chemical and biological: Accurate determination of linkages of the NANA's in the MN antigens and the linkages of the penultimate galactoses to the subjacent sugar(s), probably alpha-N-acetyl-D-galactosamine. It needs to be ruled out, however, that it is galactose. It also needs to be established if both immunodeterminant non-reducing terminal structures of the MN antigens attach to the same sugar or two adjacent ones. We will isolate for comparative purposes the MN active antigens and their precursors from human tissue. We will isolate the presumed receptor for an oncogenic virus in large quantity in order to proceed with the characterization of it. This may allow us to determine the mode of action of the inhibitory effect, we have observed, of the MN antigens towards a fowl sarcoma virus in vivo.